Data of the quantity of relatively big data are transferred between different data communication equipments connected each other in a network. These data are called bulk data or file data. Data are usually processed to a file unit. Therefore, the file is transferred by a single file unit.
On the other hand, it is studied to use a given band effectively in order to raise transfer efficiency. There is packet division technology according to UDP (User Datagram Protocol) in this one (for example, referring to patent document 1). The UDP is connectionless and is the protocol of no procedure, and has less limitation than a protocol of TCP (Transmission Control Protocol). Therefore, in the UDP, it is possible to use a band effectively by detecting a data transfer rate in a transfer state and regulating a data transfer rate dynamically.